1. Technical Field of the Invention
The present invention relates generally to methods of locating the position of sources emitting material into a fluid. More specifically, the present invention relates to methods of locating sources of airborne pollution over an area. The area is reasonably approximate to the invention.
2. Description of the Related Art
In order to legally and technically control pollution, it is necessary to locate, with reasonable accuracy, the point or points from which a pollutant is released into the biosphere. Only then can responsibility be assigned and remedial measures taken. In an industrial context, location is a difficult task because many potential sources of pollution are located together in industrial parks and the wind carries the pollutants from their source or sources in a variable manner.
In the past, many techniques have been developed to sense or locate emission sources. In broad outline, these prior methods fall into two categories: remote sensing and sample collection.
Remote sensing, whether ground-, air- or space-based, relies on detection of a physical characteristic of the pollutant, usually its electromagnetic (i.e., U.V., visible or I.R.) spectra. This spectra is monitored by either passively observing the spectra, as by airborne or satellite imaging, or by passing a laser beam through the atmosphere and observing the resultant spectra. While this method works well for some types of pollutants, it is generally not sensitive and, thus, requires a large presence of pollutants in the atmosphere to be useful. Many types of pollution do not have an optical spectra that is easily measured. Many pollutants are dangerous and illegal at concentration levels too low to be detected using current remote sensing technology. Normally, remote sensing by an optical signal establishes a measurement along a line. However, that measurement cannot typically locate the source of an airborne emission, when there is wind, if the remote sensing instrumentation is stationary, and only pointed in one direction.
Sample collection is used widely for the detection of pollutants of all kinds. The prior art teaches many systems for taking and analyzing atmospheric samples. Usually the pollutants in such samples are identified and their concentration is measured by an analytic means, e.g., a gas/liquid chromatograph. This instrument operates by passing a sample through a chromatographic column packed with an inert support upon which a nonvolatile coating has been deposited. As the sample passes through the column, individual molecules are absorbed and then released at different times from the column's surface. If a column of the proper type is employed, the components of the sample emerge from the column completely separated from each other, with the most strongly absorbed component emerging last. This emerging stream then passes through a detector, which detects each component by means of thermal conductivity, reaction to ionization, or other well known technique. The advantage of the gas/liquid chromatograph over the optical spectrometer is that it can make nearly simultaneous measurements of many components and can detect very low concentrations of pollutants in the one part per billion or trillion range. Although the chromatograph can determine what pollutants are present in a sample, it cannot provide information about the location of the source of the pollution unless many samples are analyzed from points close to the source.
The prior art teaches the use of mobile sampling stations which are usually mounted in a vehicle which traverses areas suspected of being the source of pollutants. This works well where the mobile sampler can go into the area, but it is not well suited for continuous monitoring of a site, both because of the great expense of such mobile systems and the fact that they must operate close to the emission source to make an accurate map of its location. In many cases, such as in an industrial park, refinery, chemical plant or waste dump, it is practically impossible to use a mobile sampling system because there are not enough roads inside or around the facility. In many cases, it is desirable to maintain a continuous pollution monitoring system around the industrial facility. At present, the prior art teaches systems such as stainless steel sample cans that are opened to obtain and hold atmosphere samples on a controlled basis. Such systems can only report the average concentration of a pollutant over a long period of time. They are very expensive. It is necessary to take many samples within the suspect area to reliably locate the source of emission of the pollutant.
In summary, then, the prior art teaches the location of some sources of emission of pollution by remote sensing, but this method is not effective at low levels of emission and doesn't work for all pollutants. Sample collection and analysis by gas/liquid chromatography provides high sensitivity and can measure many pollutants, but does not locate the source of emission unless many samples are taken close to the emission source.